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This article will explain in detail about MySQL 8.0 new feature flashback index is how, the quality of the article content is high, so Xiaobian share for everyone to make a reference, I hope you have a certain understanding of related knowledge after reading this article.

Oracle uses desc index in many scenarios, so I won't repeat it here. Congratulations, MySQL 8.0 also has a flashback index.

Backward index scan keyword will be seen in the execution plan. In Chinese, it is to search for the range of backward index.

mysql>explain select * from test_backup.paralleltest order by id desc+----+-------------+--------------+------------+-------+---------------+---------+---------+-----+------+----------+---------------------+| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |+----+-------------+--------------+------------+-------+---------------+---------+---------+-----+------+----------+---------------------+| 1 | SIMPLE | paralleltest | | index | | PRIMARY | 602 | | 3000 | 100 | Backward index scan |+---------------------8 ms.

innodb works only with innodb storage engines and is subject to the following limitations:

- Changebuffer is not supported if the index contains a column of descending keys, or if the primary key contains a column of descending indexes

-innodb sql parser does not use descending index

Descending index is the same as ascending index, supporting all data types

·distinct can use descending index

Descending indexes support btree, but hash indexes are not supported

Descending indexes do not support full-text indexes, spatial indexes Descending indexes support regular indexes, and gernerated columns (virtual\stored columns)

min()/max() query optimization does not optimize with indexes with descending keys when there are aggregate function calls but no group by statements

Introduction of descending index, MySQL 8.0 no longer implicitly sorts group by operations

About MySQL 8.0 new features how the index is shared here, I hope the above content can be of some help to everyone, you can learn more knowledge. If you think the article is good, you can share it so that more people can see it.

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